Tubing comprised of polymeric material is used in many industrial and commercial applications including in the medical field. Various FDA compliant plastics are used, depending upon properties desired and the intended applications. Where the tubing is used to transport fluids for in vivo treatment of human patients, selection of the polymeric materials can be a factor.
Polyvinyl chloride (PVC) is one of the most widely used plastics. While structurally stable and easily formable into desired shapes, PVC is typically manufactured using plasticizers which can migrate out of the PVC matrix into bodily fluids and has other properties not ideally suited for medical treatment applications. Likewise, due to the inherent nature of plasticized PVC tubing, there arises the potential absorption of medicines and other components of aqueous fluids used in medical treatments into the sidewall of the PVC tube. Polyurethane is potentially a substitute for PVC. However, dual layer tubing comprised of polyurethane and polyethylene suffers from the inability of the two layers to remain adhered to each other under low to moderate stress, strain or mechanical manipulation conditions as well as the inability to sufficiently impede migration of oxygen through the layers. U.S. Pat. No. 4,627,844 to Schmitt (“Schmitt”), the disclosure of which is incorporated herein by reference as if fully set forth, discloses a tri-layer tube which is embodied in a commercial product sold under the trademark “SUREPATH 151” by the Natvar Division of Tekni-Plex, Inc. As disclosed in Schmitt, an outer layer of PVC and an inner fluid-contact layer of low density polyethylene (LDPE) are co-extruded with an intermediate tie layer of ethylene vinyl acetate copolymer (EVA). However, while Schmitt greatly reduces the possibility for the migration of additives from the PVC to the fluid and absorption of components from the fluid to the PVC tubing by providing a LDPE fluid-contact layer, elimination of the PVC is preferred. Other tubing configurations are disclosed in U.S. Pat. No. 7,647,949, U.S. Pat. No. 4,211,741 and U.S. Patent Publication No. 2007/0119511, the disclosures of which are incorporated by reference as if fully set forth herein. Where medical tubing is concerned, preservation of the integrity of reagents contained in fluids being routed through the tubing can be a concern. Similarly, prevention of migration of components out of the fluids through the tubing can be an issue. In such applications, incorporation into the tubing of a layer of material comprised of a gas barrier material can be implemented for purposes of preventing migration of gases such as oxygen into the fluid thus preserving oxygen sensitive reagents in the fluid.